Designing a Storage Infrastructure for Scalable Cloud Services
Designing scalable wireless networks in the campus LAN
Transcript of Designing scalable wireless networks in the campus LAN
Designing scalable wireless networks in the
campus LAN
Sebastian Büttrich, wire.less.dk/NSRC
edit: March 2010, KENET
http://creativecommons.org/licenses/by-nc-sa/3.0/
Agenda• Introduction to wireless networking– Standards, Modes, Topologies
• Wireless Hardware– Routers & Access Points– Antennas
• Integration with a Campus LAN
• Wireless security
• Captive portals
• Wireless roaming
• LAB: hands-on wireless
Goals• Understanding the basics
• Understanding that in wireless
cost and quality are not always correlated
• See how skills and brains matter
• See that we need the same brains, whether we go
low budget or BIG BUDGET
• Develop a good feeling for layer thinking
• Work towards a set of “best practices” for campus
wireless
• And ...
Goals• Hopefully, see that low cost wireless is fun
and can bring you wonderful places :)
Learning more• http://wirelessu.org
• http://nsrc.org
• http://wireless.ictp.it/
• Wireless Training Kit (ICTP/ITU) out soon!
• The green book: http://wndw.net
The basics• Introduction to wireless networking– Standards, Modes, Topologies
• Wireless Hardware– Routers & Access Points– Antennas
Integration with a campus LAN
• All the rules and best practices for general
network architecture apply
– They matter even more in wireless, as your logical
network architecture no longer is reflected in your
physical architecture
• A user on the library network might in fact be 10
miles away!
Rules and best practices
• Build a structured network, not a flat one! Build stars
and trees, not chains or clouds
(except where you like a cloud :)
• Subnet! Subnet! Subnet!
• Reflect organisation and policies in your IP design
• Separate core and edge networks
• Planning of maximum size of subnets becomes
even more important – as the capacity of wireless cells
is limited!
Specifically wireless
• In contrast to a wired network, you now have to
consider additional planning – as your medium is now
boundless.
– Network separation on Layer 1 / 2 • by means of Frequency (Standards, Channels)
and Polarization planning
– Reach and Power planning, Antennas
– Naming (SSIDs)
Frequency planning
• If two people give you torch signals with a red torch,
you cant tell one from the other
• If one uses red, the other green – you can 'read' both
Frequency planning
Important wireless planning activities
• A Link Budget is the calculation of power – starting
with output power and including all gains and losses
(mostly for P2P, long distance links) –
no (long) link without a Link Budget!
Important wireless planning activities
• A Site Survey is the on-site recording of all relevant
conditions – from technical (e.g. finding existing
wireless networks) to human (social factors) to
environmental – no wireless deployment without
Site Survey!
Wireless on Layer 2
• The physical layer - Modes:
– Master / Station (managed mode) – typically used
for Point-to-Multipoint (P2MP):
hotspots, “access points”
– Ad-hoc:
typically used for P2P or MP2MP
• Modes do not have to match topologies!
– You might find a P2P link consisting of Master and
Client
Wireless on Layer 3
• The behaviour of wireless units with regards to TCP/IP
may be:
– Pure bridging
– Routing• DHCP, NAT, Masquerade, etc
• DHCP may be integrated with network-wide DHCP (bridge through), but separate DHCP for wireless subnets is sometimes advisable
• Again, typical behaviour on Layer 2 is not necessarily
reflected on Layer 3! Dont get confused!
Putting it all together -wired
Putting it all together -adding wireless elements
Typical roles for wireless:
• Wireless links may replace fiber/wired links in the core
network where distance or budget or security aspects
suggest this
• Wireless “hotspot” access on the edges: offices, cafes,
libraries, workspaces, ...
• Wireless mesh clouds on the edges, e.g. for
compounds, housing, villages
Putting it all together -adding wireless elements
• Design 1+ wireless here
Putting it all together -IP design
• IP design must reflect organisation and logic in order to
be manageable – especially for wireless networks
• E.g. IP subnets like this:– 10.1.0.0 Infrastructure– 10.10.0.0 University internal networks, Admin– 10.20.0.0 Students– 10.30.0.0 Open networks for guests etc
• Other IP design principles:– by location– by department– by physical carrier, e.g. wired/wireless
Putting it all together -IP design
• The important thing is that
– you are able to treat network segments in
meaningful ways (e.g. bandwidth management,
security, access time, usage rules, incident
response)
– When things go wrong, you are able to isolate and
address network segments
• This is even more important for wireless than for wired
networks! Why?
IP design for edge access
• Let us focus on edge access
• There isn't one golden rule how to do it right -
but there are several best practices to discuss
IP design for edge access
• Example 1:
aligning IP design with organisational logic
• For example, wireless access for administrative
employees
• Recommendation: place the wireless access on the
same subnet as the wired workplaces - with strict
access control, DHCP bridged through
IP design for edge access
• Example 2:
open access in cafeteria, library, etc
• Usergroup is uncontrollable
• Recommendation: – place the wireless access on separate subnet– VLAN– with access control, back end integration (e.g.
through RADIUS)– DHCP bridged through, in order to secure roaming
IP design for edge access
IP design for edge access
• Example 3 – an alternative:
open access in cafeteria, library, etc
• Usergroup is uncontrollable
• Recommendation: – Keep wireless access completely open! Consider it
“open internet”– Make sure the wireless subnet is properly isolated– Ensure access control and security on level of• Service / server• Application